Model railroad motors are powered by drawing direct current (D.C.) electricity through the rails on which the train runs, the power being conducted through the metal wheels of the model train, onto contacts that touch the metal wheels, and through wires to a small D.C. motor known in the art. The D.C. motor then converts the electric power to rotational energy, which is then transferred by a worm gear or other type of gearing to the wheels of the train motor. The use of a set of gears for transmission of power from the motor to the wheels results in a certain loss in efficiency, ultimately limiting the speed of the train. The use of a worm gear transmission also results in model train engines that characteristically stop abruptly when the power is shut off, rather than coasting to a stop gradually to simulate the action of actual railroad engines braking against substantial momentum.
It is known in the art, as an alternative to model railroad engines with gear transmissions, to provide a direct-drive model railroad engine that uses segmented wheels on the train as "rolling commutators" connected to an armature in between, as is described in U.S. Pat. No. 2,536,344 ('344 patent) to Herbert S. Bean. As shown in FIG. 1 of the '344 patent, essentially reproduced and renumbered herein as FIG. 1, such a motor comprises a permanent magnet 10, a rotatable armature 12 between the poles thereof, and two separate commutators (wheels) 14 and 16 mounted at opposite ends of the armature and adapted to ride upon a pair of rails 17. Wheels 14 and 16 are divided into a plurality of conductive segments 18, each segment being insulated from the others, and each electrically connected to a coil of the armature. Segments 18 are rigidly held between two insulating discs 20 and 22 that form part of each wheel 14 and 16, as shown in FIG. 2.
Other details of the motor are described in the '344 patent, which is incorporated herein by reference. As is apparent from FIG. 1, however, permanent magnet 10 as shown and described in the '344 patent is a standard horseshoe magnet that hangs from a bridge 24 above the motor. This placement of the magnet above the motor makes the assembled train top-heavy, and likely to tip over or derail when negotiating turns quickly. Thus, there is a need in the art for an electric model railway motor that provides the advantages of direct-drive without the top-heaviness inherent in the use of an overhead horseshoe magnet.